The simultaneous injection of intimately mixed water and air into subsurface soil is described in U.S. Pat. No. 6,173,526, issued to Angelo Mazzei. The objective is to provide both substances in proper proportions directly to the root systems of plants. The term “root system” includes roots of plants such as bushes and vines that provide their crop above the surface, and root crops in which the crop itself is considered to be the root system. Examples of the latter are potatoes, turnips, carrots and tubers.
Such mixer/injectors inject air into a water supply stream in the form of “micro bubbles” of very small size to produce an intimately “mixed stream” of water and bubbles. The bubble sizes are so small as to discourage their separating out of the water, or to aggregate together in larger bubbles. While these undesired effects are “discouraged”, and very small bubbles remain suspended in the water for long periods of time, the separation of air from the water is not completely prevented. Then, in a system which relies on simultaneous emission of air and water in an established ratio for its utility at the point of application, accumulated separated air can result in disruption of the system. In some circumstances it can entirely prevent the emission of a mixed stream of air and water in some regions of the system.
Irrigation systems of interest are sometimes called “drip irrigation”, even though the emission is underneath the surface. Systems according to this invention have proved to be very effective on commercial crops. With its use, crops such as bell peppers and strawberries have reached the market many days earlier, and thereby command premium prices compared with later product that was grown with conventional irrigation. Consistent increases in gross crop yields on the order of 10% over a season have frequently been observed. Increases as high as 30% have also been observed.
These irrigation systems are intended principally for commercial installations where one header can serve as many as 40 branches in parallel rows. Each branch may be several hundred feet long. Water and air are both fluids, and the ratio of the water to the air in the mixed stream where it is emitted into the soil is of considerable importance. If air is missing from the mixture in some parts of some branches, or if some branches emit only air, or only water, the nearby areas will produce less product, and the product may be of lesser quality. It is important that an irrigation system which extends over a broad area provide a reasonably consistent product. Unfortunately, differences in some areas may not become evident until after some damage is done. It is an object of this invention to alleviate the tendency of separated air to accumulate in local regions in the system, a situation that could impede the passage of water that is correctly laden with micro bubbles, or could cause emission of water without air, or air without water.
The principal region where this impediment may occur is in the header at one or both of its ends. At this point or points, separated air can collect and back up the system by displacing the air/gas mixture, or by injecting sudden loads of air into the stream to create hammer and inconsistency of flow. It is also possible, although less so, for separated air to accumulate somewhere in the branches. It is an object of this invention to overcome these problems.